1. Field of the Invention
This invention relates to material handling apparatus, and more particularly to an apparatus for working plate-shaped material.
2. Description of the Prior Art
Apparatus of this type is typically provided with a frame and a pair of cooperating elongated working means, one of the working means having a stationary arrangement in the frame and the other being movable in the frame, transversely to its longitudinal direction, towards and away from the stationary working means. Such devices are e.g. known in the shape of press brakes and guillotine shears, whereby the elongated means are respectively formed by cooperating stamps, by means of which the plate to be worked can be folded, or deflected, in the desired manner or by co-operating knives by means of which the plate can be sheared. Usually the elongated working means, which is movable transversely to its longitudinal direction, is thereby mounted on a beam, whereby driving means, usually in the shape of hydraulic setting cylinders, act on both ends of the beam. Such a beam must have a particularly heavy construction in practice, in order to resist undesirable deformations as well as possible. Particularly with press brakes this is very important, because undesired deformations not only may have an adverse effect on the life of the working means, but also may lead to undesirable dimensional variations in the product formed.
From the British Patent Specification No. 1,028,868, there is known a press whereby a working means having a movable arrangement in the frame can be moved by means of an inflatable bag extending along the length of the working means. Such a flexible bag is vulnerable to damage, and the movement effected by means of such a bag is difficult to control accurately.
German Patent Application 3,419,123 illustrates the principle of a press wherein the two working means are movable by means of a cable wound on the two working means. One of the disadvantages of this known construction is the poor accessibility of the space between the working means.